Graphic recorder drive assembly

ABSTRACT

A graphic recorder has a string drive for the recording pen, the string being secured to and passing around a pulley mounted to a clutch hub. A potentiometer is also mounted to the clutch hub. A servomotor drives a bull gear having a clutch ring affixed thereto. The clutch ring drives the hub through a pair of &#39;&#39;&#39;&#39;O&#39;&#39;&#39;&#39; rings, frictionally fit therebetween, the torque capacity being adjustable by an axially adjustable retainer.

United States Patent Inventor Vincent J. East Indianapolis, Ind.

Appl. No. 804,737

Filed Feb. 13, 1969 Patented Oct. 5, 1971 Assignee Esterline Corporation New York, N.Y.

GRAPHIC RECORDER DRIVE ASSEMBLY 13 Claims, 3 Drawing Figs.

US. Cl 346/139, 192/65 Int. Cl G0ld 15/16 Field of Search. 346/32,

[56] References Cited UNITED STATES PATENTS 1,216,244 2/1917 McDowell 192/65 X 2,690,246 9/1954 Kelleigh 192/66 2,931,964 4/1960 Dawe et a1 318/28 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Edith C. Simmons AnomeyWoodard, Weikart, Emhardt & Naughton ABSTRACT: A graphic recorder has a string drive for the recording pen, the string being secured to and passing around a pulley mounted to a clutch hub. A potentiometer is also mounted to the clutch hub. A servomotor drives a bull gear having a clutch ring affixed thereto. The clutch ring drives the hub through a pair of O-rings, frictionally fit therebetween, the torque capacity being adjustable by an axially adjustable retainer.

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I N VE N TOR VINCENT J. EAST A TTORNE YS Mamie/11M, M 77W 1 GRAPHIC REcoRnaR DRIVE ASSEMBLY BACKGROUND OF THE INYENTION 1. Field of the Invention This invention relates generally to graphic recorders, and more particularly to the drive assembly therein from the servomotor to the recording head.

2. Description of the Prior Art Recording instruments and other instruments are known which employ an indicating pointer or marking pen which is power driven, manually driven, or driven alternatively by either power or manual means. In many instances, such instruments employ a string or cord drive, and a potentiometer associated with it. A problem can arise if the input to the instrument, whether it be manual or powered, is such as to cause the indicator or pen to be driven off scale, or to cause excessive rotation and damage to a potentiometer. Several means have been attempted to prevent the damage to components. One well-known and early approach was to wrap the string loosely enough around a knob or pulley that no damage could be done. Where recording instruments are relied upon for rapid and accurate representations of drive motor movement, such approaches are relatively unsatisfactory. Other efforts have been made to employ clutches of the slip type to avoid damage.

Example of clutches, brakes, and dampers which involve various types and possibilities for slippage and release can be found in the following United States Patents: I

2,690,246 Kelleigh Sept. 28, I954 2,927,672 Banner Mar. 8, 1960 2,927,674 Everitt Mar. 8, I960 3.034.625 Grote May 15, I962 3,092,23l Kneuu June 4, 1963 3,148,756 Romanini Sept. 15, I964 3,263,45l Reimer Aug. 2, I966 3,385,082 Deuring et al. May 28, 1968 Some of the problems confronting a person attempting to adapt such equipment to the environment of interest, are immediately' obvious. Another problem involves obtaining a large available range of release torque adjustment with a minimum range of clamping force required. Other problems involve space requirements and costs. Still another requirement is consistent performance over a relatively long useful life. The present invention is directed to the solution of these problems.

SUMMARY OF THE INVENTION Described briefly, in a typical embodiment of the present invention, a large gear driven by a servomotor of a recording instrument is provided with a surface facing inwardly toward a hub which is connected to the pen string drive pulley of the instrument, and also to a potentiometer. A pair of O"-rings is provided between the facing surfaces of the ring and hub, the rings being under radial compression to permit torque transmission from the gear to the drive string and potentiometer. An axial adjustment is provided to apply an axial crush on the rings to establish and maintain the radial compression at a level producing the desired torque-transmitting capacity. This is adjusted so that the clutch thereby produced will slip when the pen is driven off scale in either direction by the servomotor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a top plan view of a portion of a recording instrument incorporating a typical embodiment of the present invention.

FIG. 2 is a view taken at line 2-2 in FIG. 1 and showing the rear elevation of the central portion of the large gear and clutch assembly, but omitting the coupling member 24.

FIG. 3 is a section through the assembly taken at line 3-3 in FIG. 2 and viewed in the direction of the arrows, and showing a portion of the coupling member 24 but omitting the string-driye pulley 19 of FIG. I.

Referring now to the drawings in detail, and particularly FIG. 1, a chart recorder is provided with a mechanism frame 11 having a backplate 12 to which is mounted a servomotor 13, along with a potentiometer 14. The servomotor drives a pinion 16 engaged with a large bull" gear 17. The central axis 18 of gear 17 is collinear with the potentiometer axis and the gear is supported in a manner which will become apparent as the description proceeds.

A string drive pulley l9, concentric with axis 18, has the drive string 21 connected thereto and passed therearound and around additional pulleys 22 of the mechanism frame and connected to the indicator marker and pen assembly 23.

A coupling member 24 is secured to the potentiometer shaft 26 with means provided to prevent relative rotation therebetween; a setscrew or matching flats being a suitable arrangement. As better shown in FIG. 2, considered with FIG. 3, the frontal portions of the coupling member 24 are received in concentric apertures 27 and 28, with a pin 29A of the coupling member being received in the aperture 29' of the clutch hub 31 to prevent relative rotation between the parts. Suitable bearing means 32 are provided between the hub and the clutch ring 33 to which the gear 17 is afflxed, whereby the entire assembly is supported for rotation on the axis 18.

The clutch hub member 31 has a radially extending circular flange 34 thereon extending outward from the surface on which the bearing 32 rotates and also extending outward from an outer cylindrical surface 36 which extends towards the flange from the rear face 37 of the clutch hub member 31. An -ring 38 encircles this surface 36. Similarly, an O"-ring 39 encircles an outer cylindrical surface 41 of the retainer ring 42 having the radially extending circular flange 43 thereon. These "-rings may be made of rubber or some other suitable elastomeric or polymeric substance. Three screws 44 are threadedly received in axially extending threads in the clutch hub member 31, and the screw heads bear on the rear face 46 of the retainer ring. The screw slots are exposed at the face of the ring for easy access.

By tightening the three screws 44, the O"-rings are squeezed between the flanges 34 and 43 causing radial compression thereof in the direction of arrows 47-48 against the inner and outer cylindrical surfaces respectively of the clutch ring 33 and the clutch hub and retainer members 31 and 42, respectively. The amount of this radial compression determines the torque transmission capability of the assembly from the gear 17 to the hub 31, and thereby through the aperture 29 and pin received therein to the potentiometer and tothe pulley 19, the latter having an aperture matching the aperture 29 to receive the pin 29A of the coupling member on which the clutch hub 31 andpulley 19 are piloted.

The present invention allows the servomotor to continue to drive after a full-scale indicator or pen movement has occurred, without damaging any components of the servosystem. It is a low-cost, high-reliability, space-saving system. It will operate as well in either direction and there is essentially no slippage or distortion upon sudden reversal of servomotor rotation. The radial application of the friction members against the inner and outer surfaces of the clutch members is advantageous, and the differences in axial clamping force required to obtain large differentials in torque capacity are comparatively small. The space requirement is minimal and as the clutch wears, there is more surface contact tending to off set the smaller diameter, providing a degree of automatic compensation or self-adjustment for wear.

What is claimed is:

1. In a graphic recorder, the combination comprising:

a servomotor a first rotatable member driven by said servomotor and having an inwardly facing clutch surface;

a second rotatable member having an outwardly facing surface; a friction member between said inwardly and outwardly facing surfaces 'and constantly engaging said surfaces for torque transmission from said servomotor through said first rotatable member and said friction member to said second member;

said surfaces having a spaced relationship of a fixed dimension independent of said friction member;

and means for adjusting the torque-transmitting capability of said friction member.

2. The combination of claim 1 wherein:

said servomotor is reversible,

said friction member is compressed between said surfaces,

and

axial adjustment means are provided on said friction member to vary the degree of compression of said friction member between said surfaces to thereby vary the torque transmission capability of said servomotor to said second rotatable member.

3. The combination of claim 2 and further comprising:

a record marker coupled to said second rotatable member and drivable thereby.

4. The combination of claim 3 wherein:

said inwardly and outwardly facing surfaces are cylindrical,

and said friction member is a rubber O"-ring.

5. A clutch assembly comprising:

a first rotatable member having an inwardly facing clutch surface;

a second rotatable member having an outwardly facing clutch surface;

bearing means mounting said first member to said second member and accommodating relative rotation between said first member and said second member about a common axis;

a friction member compressed between said first and second members to facilitate torque transmission between said first and second members by said friction members;

and adjustment means operable on said friction member to adjust the compression thereof between said first and second members to influence the torque transmission capacity of the clutch assembly.

6. The clutch assembly of claim 5 wherein:

said friction member is an elastomer.

7. The clutch assembly of claim 5 wherein:

said friction member is an O-ring.

8. The clutch assembly of claim 5 wherein:

said adjustment means include a third rotatable member secured to said second rotatable member and rotatable therewith, said adjustment means being axially adjustable to increase and decrease the compression of said friction members between said members.

9. A clutch assembly comprising:

a first rotatable member having an inwardly facing clutch surface;

a second rotatable member having an outwardly facing clutch surface;

a friction member compressed between said first and second members to facilitate torque transmission between said first and second members by said friction member;

and adjustment means operable on said friction member to adjust the compression thereof between said first and second members to influence the torque transmission capacity of the clutch assembly;

said inwardly facing surface is an inner cylindrical surface;

said outwardly facing clutch surface is an outer cylindrical surface coaxial with said inner surface and inwardly spaced therefrom,

said second member has a shoulder extending radially outward from said outer cylindrical surface toward said inner surface,

said adjustment member has an outer cylindrical surface coaxial with said inner cylindrical surface and spaced radially inwardly therefrom, said adjustment member has a shoulder extending radially outward from the outer cylindrical surface thereof and facing said shoulder of said second member,

a second friction member is compressed between said inner surface of said first member and said outer surface of said adjustment member,

said first and second friction members being sandwiched between said shoulders, whereby axial reduction of the space between said shoulders increases the compression of said friction members between said inner and outer cylindrical surfaces.

10. The clutch assembly of claim 9 wherein:

said adjustment member is connected to said second member by a plurality of circularly spaced axially extending screws, said screws having turning tool receivers exposed at a face of said adjustment member.

11. The clutch assembly claim 10 wherein:

said first member has an external gear mounted thereon, said gear being coupled to a drive motor, and said second member has indicator means coupled thereto.

12. The clutch assembly of claim 1 1 wherein:

said second member has a potentiometer connected thereto.

13. The combination of claim 2 wherein:

said axial adjustment means include axially spaced flange means and axially extending screw means, said friction member being axially squeezed between said flange means, and said screw means being adjustable to predetermine the amount of squeeze between said flange means. 

1. In a graphic recorder, the combination comprising: a servomotor a first rotatable member driven by said servomotor and having an inwardly facing clutch surface; a second rotatable member having an outwardly facing surface; a friction member between said inwardly and outwardly facing surfaces and constantly engaging said surfaces for torque transmission from said servomotor through said first rotatable member and said friction member to said second member; said surfaces having a spaced relationship of a fixed dimension independent of said friction member; and means for adjusting the torque-transmitting capability of said friction member.
 2. The combination of claim 1 wherein: said servomotor is reversible, said friction member is compressed between said surfaces, and axial adjustment means are provided on said friction member to vary the degree of compression of said friction member between said surfaces to thereby vary the torque transmission capability of said servomotor to said second rotatable member.
 3. The combination of claim 2 and further comprising: a record marker coupled to said second rotatable member and drivable thereby.
 4. The combination of claim 3 wherein: said inwardly and outwardly facing surfaces are cylindrical, and said friction member is a rubber ''''O''''-ring.
 5. A clutch assembly comprising: a first rotatable member having an inwardly facing clutch surface; a second rotatable member having an outwardly facing clutch surface; bearing means mounting said first member to said second member and accommodating relative rotation between said first member and said second member about a common axis; a friction member compressed between said first and second members to facilitate torque transmission between said first and second members by said friction members; and adjustment means operable on said friction member to adjust the compression thereof between said first and second members to influence the torque transmission capacity of the clutch assembly.
 6. The clutch assembly of claim 5 wherein: said friction member is an elastomer.
 7. The clutch assembly of claim 5 wherein: said friction member is an ''''O''''-ring.
 8. The clutch assembly of claim 5 wherein: said adjustment means include a third rotatable member secured to said second rotatable member and rotatable therewith, said adjustment means being axially adjustable to increase and decrease the compression of said friction members between said members.
 9. A clutch assembly comprising: a first rotatable member having an inwardly facing clutch surface; a second rotatable member having an outwardly facing clutch surface; a friction member compressed between said first and second members to facilitate torque transmission between said first and second members by said friction member; and adjustment means operable on said friction member to adjust the compression thereof between said first and second members to influence the torque transmission capacity of the clutch assembly; said inwardly facing surface is an inner cylindrical surface; said outwardly facing clutch surface is an outer cylindrical surface coaxial with said inner surface and inwardly spaced therefrom, said second member has a shoulder extending radially outward from said outer cylindrical suRface toward said inner surface, said adjustment member has an outer cylindrical surface coaxial with said inner cylindrical surface and spaced radially inwardly therefrom, said adjustment member has a shoulder extending radially outward from the outer cylindrical surface thereof and facing said shoulder of said second member, a second friction member is compressed between said inner surface of said first member and said outer surface of said adjustment member, said first and second friction members being sandwiched between said shoulders, whereby axial reduction of the space between said shoulders increases the compression of said friction members between said inner and outer cylindrical surfaces.
 10. The clutch assembly of claim 9 wherein: said adjustment member is connected to said second member by a plurality of circularly spaced axially extending screws, said screws having turning tool receivers exposed at a face of said adjustment member.
 11. The clutch assembly claim 10 wherein: said first member has an external gear mounted thereon, said gear being coupled to a drive motor, and said second member has indicator means coupled thereto.
 12. The clutch assembly of claim 11 wherein: said second member has a potentiometer connected thereto.
 13. The combination of claim 2 wherein: said axial adjustment means include axially spaced flange means and axially extending screw means, said friction member being axially squeezed between said flange means, and said screw means being adjustable to predetermine the amount of squeeze between said flange means. 